Clamping circuit

Abstract

The invention provides a clamping circuit which is integrated inside a low-voltage MCU chip. The clamping circuit comprises a low-voltage NMOS pipe and a low-voltage PMOS pipe. A source electrode of the low-voltage NMOS pipe is connected with a low-voltage power source in the chip, and a substrate of the low-voltage NMOS pipe is connected with ground. A source electrode of the low-voltage PMOS pipe is connected with the ground, a substrate of the low-voltage PMOS pipe is connected with the low-voltage power source, and a drain electrode of the low-voltage PMOS pipe is connected with a drain electrode of the low-voltage NMOS pipe. A voltage leading-out point is formed on the connecting point of the drain electrode of the low-voltage PMOS pipe and the drain electrode of the low-voltage NMOS pipe, and the voltage leading-out point is connected with a high-voltage alternating-current level outside the chip. According to the clamping circuit, high-voltage alternating current signals which are excessive in amplitude are clamped within the largest withstand-voltage range which the low-voltage MCU chip can bear, and therefore an over-zero comparison function is integrated in a CMOS low-voltage technology, external elements are reduced, and cost is lowered.

Description

Technical field [0001] The present invention relates to the technical field of analog integrated circuit design. Specifically, the present invention relates to a clamp circuit applicable to zero-crossing detection. Background technique [0002] 1) Current product structure [0003] At present, the zero-crossing detection function applied to the SCR / relay control in the field of large and small home appliances is realized by integrating external components outside the low-voltage chip and on the PCB board. figure 1 with figure 2 . The meaning of zero-crossing detection is: the detection of the zero phase of the detected signal and a certain reference signal, that is, the voltage detection when the voltage is equal. [0004] 2) The principle of the current product [0005] Attached figure 1 The principle of the high-voltage zero-crossing detection application circuit shown in is: the detected signal is a high-voltage signal, which is stabilized below a certain voltage VCM through the ...

AI Technical Summary

Problems solved by technology

[0009] a. For the low-voltage MCU chip of CMOS process, it cannot directly withstand the mains AC 220V / 110V voltage and other forms of high voltage. figure 1 , 2 The diode D1 and transistor J1 are integrated in the chip, so it is necessary to integrate external components on the printed circuit board (PCB) to realize the AC zero-crossing detection function during application, which increases the cost of the user's application and the complexity of the application circuit degrees while increasing the area of ​​the PCB

[0010] b. Due to the use of external components and applications in high-voltage circuits, they are susceptible to interference

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